This dark spot on the surface of Jupiter is the shadow of its most volcanic moon, Io. To wit:
Since Jupiter shines predominantly by reflected sunlight, anything that blocks that light leaves a shadow. If you could somehow be in that shadow, you would see a total eclipse of the Sun by Io. Io‘s shadow is about 3600 kilometres across, roughly the same size as Io itself — and only slightly larger than Earth’s Moon. The featuredimage was taken last month by NASA’s robotic Juno spacecraft currently orbiting Jupiter. About every two months, Juno swoops close by Jupiter, takes a lot of data and snaps a series of images — some of which are made intoa video. Among many other things, Juno has been measuring Jupiter’s gravitational field, finding surprising evidence that Jupiter may be mostly a liquid. Under unexpectedly thick clouds, the Jovian giant may house a massive liquid hydrogen region that extends all the way to the centre.
Reuters reports on an innovative new project at the Norwegian town of Rjukan – located at the base of a narrow valley and starved of sunlight for six months of the year.
The brainchild of local artist Martin Anderson, the plan involves three heliostat mirrors positioned at the top of the hill that will reflect a patch of SAD-dispelling sunlight into the town square all Winter long.